Cement is one of the most widely used substances on the planet. Unfortunately, it is also one of the most polluting, accounting for about 5-7% of all CO2 emissions. There are two major sources of CO2 resulting from the production of cement. The first results from the fuel burned to produce extremely high (1450° C.) kiln temperatures needed to modify the raw materials. The second source of CO2 results from calcination of limestone, which is the main binding agent of the cement. With increased focus on global warming and sustainable construction methods, environmentally friendly cement will become even more important in the future.
New binding agents and processing methods can reduce the amount of CO2 generated in the production of concrete and mortar. Today, the binding agent in the most concrete and mortar is Ordinary Portland Cement (OPC), which is made by heating limestone and other materials extremely hot (1450° C.) kilns. Other current methods for reducing emissions includes the use of renewable fuels in the kiln, improved kiln efficiency and the addition of fly ash and slag as cement substitutes. Although the solutions are beneficial, they have drawbacks. For example, the use of alternative fuels adds cost, further kiln efficiency gains will likely be limited and current building codes restricts the amount of OPC-substitute materials that can be used in the construction projects.
As the world's regulatory agencies increase their focus on reducing human-generated CO2, new cement alternatives could find a ready market, particularly as cement consumption continues to rise, especially in developing countries. However, “green” alternatives to traditional cement will need to have strength, handling, durability, and other characteristics that are similar to OPC at a similar cost. This is particularly relevant in developing nations, which will be unwilling or unable to support green alternatives that cover significant cost premiums compared to traditional products. Yet, the new compositions should have at least similar properties of Portland cement.